Hardy zeta

5.1. The critical line🔗

def criticalPoint (t : ℝ) : ℂ := 1 / 2 + t * Complex.I

The function criticalXi restricts xi to this line. The theorem criticalXi_eq_zero_iff relates its zeros to the zeta zeros. The theorem criticalXi_im proves that its imaginary part is zero. The function hardyXi gives its real value.